When using a DC filament supply, why is it advisable to periodically reverse the polarity?

When using a DC filament supply, why is it advisable to periodically reverse the polarity?

• A. To lengthen the life of the filament
• B. To increase the efficiency of power supply
• C. To prevent overheating of the filament
• D. None of the above

Answer: (A)

Periodic reversal of polarity in a DC filament supply helps to lengthen the life of the filament. This technique is based on the principle that reversing the current can mitigate the accumulation of contaminants and uneven wear on the filament. Over time, the operation of a filament can lead to the deposition of materials on its surface and cause it to become uneven. By periodically reversing the polarity, the current direction changes, which can help to evenly distribute wear and prevent the filament from developing hot spots or becoming weak in one area. This leads to more uniform heating of the filament and can extend its operational lifespan, as well as improve overall performance. While there may be considerations about efficiency and overheating, the primary benefit of polarity reversal is the preservation and longevity of the filament itself.

Periodic reversal of polarity in a DC filament supply helps to lengthen the life of the filament. This technique is based on the principle that reversing the current can mitigate the accumulation of contaminants and uneven wear on the filament.

Over time, the operation of a filament can lead to the deposition of materials on its surface and cause it to become uneven. By periodically reversing the polarity, the current direction changes, which can help to evenly distribute wear and prevent the filament from developing hot spots or becoming weak in one area. This leads to more uniform heating of the filament and can extend its operational lifespan, as well as improve overall performance.

While there may be considerations about efficiency and overheating, the primary benefit of polarity reversal is the preservation and longevity of the filament itself.